Chelsea defender Gary Cahill admitted a hard day at the office was no less than the European champions had expected after being held to an FA Cup fourth round 2-2 draw at Brentford on Sunday.

Boss Uwe Rosler's Bees twice took the lead through Marcello Trotta and a Harry Forrester penalty - which came 17 minutes from time - only for a late Fernando Torres strike to rob the League One side of a historic win.

Chelsea, third in the Premier League, were poor in the first half, but recovered to make sure their name was in the hat for the fifth round draw.

Boss Rafael Benitez's men will travel to Middlesborough in the next round should they see off the Bees at the second time of asking on February 17.

And Cahill reckoned his side must improve for the replay at Stamford Bridge.

"They made it very difficult for us. The conditions were horrible and we needed to grind out a result, which we did in the end," he said.

"We knew it (our performance) was below par at half time. We spoke about that and we knew we had to do something about it.

"It was not an enjoyable game, but we got the result we wanted. Now we need to show our quality at home.

"We were not surprised by Brentford. When you come to places like this it is their cup final in a way.

"The reserves play here so we knew the pitch was not going to be good. It was hard for us to play our passing game.

"They worked hard, put us under pressure and we found it difficult at times, so credit to them."

Benitez, who bemoaned the decision not to award his side a penalty late in the game when Juan Mata's cross struck Bees defender Harlee Dean's hand from close range, was equally relieved.

"We knew it would be difficult. We made too many mistakes in the first half, but I was pleased with the team's reaction in the second half and disappointed the penalty was not given," he said.

"I was impressed with the character they (Brentford) showed. The manager knew what he wanted his side to do and they did it, so credit to them."

It proved to be a weekend of cup shocks involving former Brentford players with Robbie Simpson in the Oldham Athletic side that beat Liverpool 3-2 at Boundary Park.

While fellow ex-Bee Paul Buckle managed Blue Square Premier side Luton Town to a memorable 1-0 triumph at Premier League Norwich City.